The development of integrated electricity and heat system (IEHS) promotes the renewable energy penetration and the complementary coupling between the electric power system (EPS) and the district heat system (DHS). The efficient energy flow calculation (EFC) in the IEHS has become a hotspot as the system scale and complexity increase. This paper firstly constructed the dynamic DHS model using Euler difference scheme. On this basis, the fast decomposed method is proposed to decompose the system with various scales and topologies, which improves the computation efficiency. Moreover, the modification mode is then developed to modify the EFC results in the decomposed systems and ensure the accuracy. Numerical simulation verifies the accuracy of the proposed method and its superiority in computation efficiency.
